Transportation and labor costs make up a significant part of a food processor's costs. Today's food products are commonly moved long distances by truck or railcar. Forklifts are used to load and unload these vehicles--which enable lifting and moving bulk quantities of food products on pallets--and thereby reduce labor costs. Even so, in some cases, significant labor is still required to load and unload these vehicles.
Because of product density or reasons attributable to the type or strength of the packaging used, some food products cannot be stacked two or more pallets high (i.e., with one pallet sitting directly on top of the pallet below). Refrigerated orange juice is a good example of this type of product. Much of the orange juice currently sold in the United States is packaged as liquid juice in low-strength plastic or paper "milk carton" containers. If pallets of orange juice packaged in this way are stacked on top of each other, the weight of the upper pallet crushes the packaging on the pallet below.
When liquid orange juice is shipped in a railcar, the interior volume of the car is usually filled side-to-side, one row at a time, with loaded pallets. The first pallets (typically two wide) are placed in a row across the cargo floor. Wooden beams are then placed cross-wise above them. The beams are supported at each end by rails that run along the length of the inside of each sidewall. Another upper layer of pallets is then loaded onto the beams--creating a stack of "two by two" pallets. The beams prevent the weight of the upper layer from pressing down on the pallets below. This is repeated four pallets at a time, from opposite ends of the car to the doorway space in the center, until the car is filled from end to end. The doorway space is not double-stacked.
The crossbeam system described above has disadvantages. It makes loading and unloading more labor intensive than in situations where product packaging has sufficient strength to allow pallets to be directly stacked one on top of another. Workers have to put the crossbeams in place gradually as the car is loaded. Likewise, the beams need to be removed gradually as the car is unloaded. During loading and unloading, the workers have to move many of the beams from inside to outside of the car to make room for a forklift. The crossbeam system also requires that a large quantity of beams travel with the car at all times. Wooden beams warp and crack in time or simply become misplaced. The loading process can be delayed if a car does not have an adequate supply of good beams.
There are safety issues with the crossbeam system as well. Lifting and carrying wooden beams can lead to back injuries or other kinds of injuries. In the modern workplace, employees frequently sue employers over accidental workplace injuries.
The invention described here relates to a pallet racking system that I developed for the purpose of eliminating the crossbeam system. While my system was developed as an improvement for use in my cryogenic railcar fleet, as described below, my system will work equally well in other types of railcars or large, transportable shipping containers. This should be self-evident from the following description. Nevertheless, in order to give the development of the invention proper context, it will be helpful to explain why the system was developed for my cryogenic railcar fleet.
Cryogenic railcars have a unique construction that is significantly different from "mechanically" refrigerated railcars. A cryogenic railcar is an insulated railcar that has an overhead ceiling bunker compartment for holding carbon dioxide (CO.sub.2) snow. CO.sub.2 snow is manufactured directly in the bunker by a manifold structure that extends the length of the bunker. Liquid CO.sub.2 is piped into the manifold and sprayed into the bunker ("bunker charging") through a series of orifices. During bunker charging, some of the spray is converted directly into CO.sub.2 snow that accumulates in the bunker. The remainder becomes cold CO.sub.2 gas.
The floor of the bunker (which is also the ceiling of the railcar's lading compartment) holds the snow as it accumulates. The bunker floor is made of a series of insulated fiberglass panels ("bunker panels"). Each bunker panel has vents that allow CO.sub.2 gas to flow from the bunker compartment down into the lading compartment. The car is "precooled" by CO.sub.2 gas from the manifold during the bunker charging process. Thereafter, sublimation of the accumulated CO.sub.2 snow in the bunker creates an ongoing supply of cold gas that keeps the car's cargo chilled or frozen while in transit. Cryogenic railcars are passive refrigeration systems and need an adequate amount of CO.sub.2 snow accumulation in the bunker in order to keep the load chilled or frozen while the car is in transit over a period of many days.
The basic cryogenic design described above is illustrated in U.S. Pat. No. 4,704,876 ("the '876 patent") issued to Ralph Hill on Nov. 10, 1987. The '876 patent is incorporated in this document by reference. My company owns the '876 patent.
Because the temperature of CO.sub.2 gas and snow are well below freezing, my cryogenic fleet was originally designed to haul frozen food products. The pallet racking design that is described and claimed here arose from my ongoing efforts to commercialize a cryogenic car that can haul food products at a refrigerated temperature without freezing them. At the present time, I am uncertain if the pallet racking system I have designed contributes to the overall thermodynamic operation of the "refrigerated" version of my cryogenic cars. However, it is certain that my pallet racking system eliminates the above labor, safety, and cost drawbacks associated with stacking certain kinds of food products in railcars and similar transportation vehicles.
Pallet racking systems have been used in warehouses for years. However, it is not feasible to put a system built for a warehouse into a railcar. Railcar's pose different design problems. Warehouse systems are made from steel--the strongest material available. Steel is obviously the material of choice because it is suitable for supporting the heaviest pallet loads.
The maximum loaded weight of a railcar is limited by government regulation and is based on the structural load limits that a railcar can carry on tracks. The same kind of limitations apply to truck traffic on highway surfaces. Therefore, putting a warehouse pallet racking frame into a railcar, or a similar transportation vehicle, is not an obvious expedient for at least two reasons. First, the weight of a steel frame decreases the load carrying capacity of the car and, hence, the amount of product that can be carried. Second, unlike a warehouse, where it may be desirable to have moveable racking systems, it is not possible to simply build an independent frame structure into a railcar by resting the framework on the cargo floor. Like any vehicle, railcars shift as they move along the rails and a racking system that supports a heavy load will be subject to high levels of dynamic force caused by movement of the car--over and above simply supporting the weight of the load. This suggests that the framework should be made of steel and built into or tied to the structural framework of the car. Steel is undesirable for the reason just stated. Building the framework into the car is not something that is easy to do as a retrofit.
My racking system overcomes the drawbacks to the crossbeam system described above. While my system, as described below, was designed for use in my cryogenic railcar fleet, and consequently, is described below in the context of a cryogenic railcar, it is to be understood that the system could be used in other kinds of shipping containers (e.g., mechanical railcars, truck trailers, large Sea-Land containers, etc.). Bearing this in mind, my present intention is to obtain the broadest patent coverage possible for any transportable shipping container.